1. Field of the Invention
This invention relates to laser medical device in general and in particular it relates to medical devices for no-contact perforation of the skin of a patient for taking blood samples.
2. Description of the Prior Art
Capillary blood sampling is a process for obtaining blood samples from the sub-dermal capillary beds of patients. The traditional methods for the collection of small quantities of blood from patients utilize mechanical perforation of the skin with sharp devices such as metal lancet or needle. This procedure has many drawbacks, two of which are the possible infection of health-care workers or the public at large with the device used to perforate the skin, and the costly handling and disposal of biologically hazardous waste.
Lasers have been used as an efficient precise tool in a variety of surgical procedures. Among sources of laser radiation, the rare-earth elements such as, for example, YAG (yttrium aluminum garnet) crystal doped with erbium (Er) ions are of interest for medicine.
As an active medium one can use various lasant materials to produce different wavelengths of laser light. These materials include, but are not limited to, rare-earth-doped oxide and fluoride laser crystals and glasses. Such crystals and glasses will be doped with impurities to fix the resultant wavelength of the laser.
In the case of lasers, the systems thereof generally include a light source for generating laser light, and optical components for directing the laser beam to a target. The laser source may produce continuous or pulsed laser energy output. The delivery of laser energy to a target specimen and subsequent vaporization of a portion of the specimen often produces byproducts, such as smoke, carbonized particles and/or splattered particles from the specimen. These byproducts pose a threat to the consistent operation of the laser system in that they may be deposited upon the objective optics of the system, thus damaging or altering the optical components, reducing output power, distorting the pattern of energy distribution within the light or laser beam, or otherwise contributing to the degradation of the system.
Methods and devices adapted for perforation of a skin tissue of a patient by means of a focused laser beam have been known in the prior art. The skin perforation is most effective when the wavelength of laser irradiation and the area of intensive absorption of optical emission by living tissue are matched. It is also important to prevent coagulation of a blood during treatment of life tissue by a laser beam. This can be achieved when yittrium-aluminum-erbium-garnet laser with laser emission wavelength of 2.94 microns and laser impulse duration between 50 and 500 microseconds is utilized by the perforation device. In the prior art perforation occurs when a laser beam is focused on the skin tissue, so that a small patch of skin at the area of focusing of the laser beam is evaporated.
Operation of certain medical devices for no-contact perforation of the skin of a patient while taking blood samples often produce significant pain and cause fear and apprehension in patients who anticipated a painful experience. Although modern designs of laser perforation devices attempted to eliminate such pain and apprehension, further reduction of patient discomfort would significantly increase the usefulness of new capillary sampling techniques. In the method and apparatus disclosed by U.S. Pat. No. 5,908,416, an attempt has been made to reduce pain in the course of perforation by providing a laser beam having a special shape. However, this approach increases the complexity of the optical system, leads to losses of the laser beam energy, makes the apparatus more expensive and difficult to manufacture. In this device, the increase in compensation of the laser energy should result in higher laser beam divergence ultimately causing skin burns at the area of perforation.
Thus, it has been a need for a laser perforation device capable of reducing pain and apprehension experienced by patients during the blood sampling procedures. It has been also a need for laser perforation devices which are protected from contamination by the products of skin tissue viporization.
One aspect of the invention provides a laser perforator for perforation of a skin of a patient and obtaining of blood samples. The perforator comprises a laser light source for producing an output laser beam, a focusing arrangement for focusing the output laser beam at the skin area selected for perforation, a guiding arrangement and a power supply unit. A retaining arrangement is provided for intensifying blood circulation in the skin area selected for perforation. The skin retaining arrangement consists of a substantially hollow intermediate region formed with a flexible peripheral wall. The intermediate region is interposed between a forwardly positioned engaging cup and rearwardly located base wall. A base member is positioned within the substantially hollow intermediate region between the engaging cup and the base wall. The flexible peripheral wall is deformable to substantially reduce a volume of the intermediate region causing pressure increase thereinside. The skin retaining arrangement also includes a pressure adjustment device for pressure adjustment within the intermediate region. After the pressure adjustment has taken place, a low pressure zone is formed within the intermediate region, so as to create suction for bringing at least a portion of the skin area deeper into the engaging cup. The pressure adjusting arrangement can be in the form of a valve and the biasing member is provided to facilitate a return of the deformed intermediate region to its initial undeformed position.
As to another aspect of the invention, the rear wall of the engaging cup is formed with an opening provided for passage of the laser beam. An optical membrane preventing fluidal communication between the engaging cup and an inner area of the perforator containing the laser source and the focusing arrangement can be provided with the opening. The shield is made of a material translucent to the laser irradiation.
As to a further aspect of the invention, a laser energy delivered to the skin of a patient can be adjusted by means of an optical member having the variable thickness along its length. The optical member is made of a material having predetermined laser irradiation transmission characteristics. The optical member is positioned between the skin area to be perforated and the laser source. The optical member can have a wedge-shaped configuration with a substantially cylindrical outer wall and can be rotationally positioned between the laser source and the focusing arrangement. In another embodiment of the invention, the optical member is moved transversely to the direction of the laser beam.
A still another aspect of the invention provides a device which prevents unintended activation of the perforator. This device comprises a plurality of independent engaging segments slidably arranged along the longitudinal axis of the cup. The distal portion of the segment forms a part of a switch operable between open and closed positions. In the open position, the distal portions of the engaging segments are spaced from a conductive plate position at a rear wall of the engaging cup, so as to disconnect an electrical supply line of the laser source. In the closed position, the distal portions of the engaging segments engage the conductive plate, so as to activate the electrical supply line of the laser source. The device can include a sliding member movable within a plane transverse to the direction of the laser beam, so that in a standard position of the device the sliding member blocks a central passage of the perforator preventing an accidental discharge of the laser beam.
The engaging cup can be formed with a substantially hollow interior cavity and is defined by at least a side wall thereof. An engaging aperture can be formed within the side wall, so that the laser beam entering the substantially hollow interior area is directed tangentially to the skin area protruding through the engaging aperture, so as to generate an elongated slit within the perforated area of the skin. Alternatively, the engaging aperture adapted for receiving the skin area can be formed at the front portion of the engaging cup, so as to be positioned at an angle to the direction of the laser beam entering the interior area.